Abstract:

Article Preview

Characterization of post implantation annealing steps is done by extracting the activation
and compensation data of implanted Al atoms. Usually, this is done by Hall measurements. The
preparation of Hall samples and temperature dependent Hall measurements, however, are rather
complex compared to, e.g., temperature dependent resistivity measurements by 4-point probing.
Therefore, a model for extracting relevant electrical parameters from resistivity data has been developed.
The model is based on the neutrality equation and a temperature dependent mobility model.

Abstract: Technological aspects of ion implantation in SiC device processes are described.
Annealing techniques to suppress surface roughening of implanted SiC (0001) are demonstrated. Trials to achieve a low sheet resistance are described for n-type and p-type doping. Implantation into the (11-20) face is also presented. Electrical behaviors of implants near implanted tail regions are discussed based on experiments.

Abstract: The authors have investigated electrical behavior of implanted Al and B atoms near a “tail” region in 4H-SiC (0001) after high-temperature annealing. For aluminum-ion (Al+) implantation, slight in-diffusion of Al implants occurs in the initial stage of annealing at 1700 °C. Nearly all of implanted Al atoms, including the in-diffused Al atoms were activated by annealing at 1700 °C for 1 min. Several electrically deep centers are formed by Al+ implantation. The concentrations of the centers are 3-4 orders-of-magnitude lower than that of implanted Al-atom concentration. For boron-ion (B+) implantation, significant out- and in-diffusion of B implants occur in the initial stage of annealing at 1700 °C. Most of the in-diffused B implants work as B acceptors. A high density of B-related D center exists near the tail region. To suppress the B diffusion, a ten-times higher dose of carbon-ion (C+) co-implantation is effective. However, high concentrations of additional deep centers
are introduced by such high-dose C+ co-implantation.

Abstract: Aluminum ions (Al+) were implanted at room temperature or at 500°C into n-type 4HSiC.
The implantation damage (displaced Si atoms) and the electrical activation of Al+ ions
(concentration of Al acceptors) were determined by Rutherford backscattering in channeling mode
and Hall effect, respectively, as a function of the annealing temperature.

Abstract: Boron (B) ions were implanted into 4H-SiC. In order to avoid the out-diffusion of B ions during the subsequent annealing process, two processing techniques were applied. Either a box-shaped B-profile was implanted, which was followed by a two-step annealing (900°C for 120 min + annealing temperature TA for 30 min), or a box-shaped B-profile was implanted together with two carbon (C) Gaussian profiles located on both edges of the B box-profile followed by a one-step annealing (TA for 30 min). The annealing temperature TA ranged from 1500°C to 1750°C. The electrically activated B acceptor concentration was measured by temperature-dependent Hall effect and the energy for the formation of the B acceptor was determined assuming a first order process.

Abstract: We propose an empirical model to predict electrical activation ratios of aluminium- and boron-implanted silicon carbide with respect to various annealing temperatures. The obtained parameters and model extensions are implemented into Silvaco’s Victory Process simulator to enable accurate predictions of post-implantation process steps. The thus augmented simulator is used for numerous simulations to evaluate the activation behavior of p-type dopants as well as for the full process simulation of a pn-junction SiC diode to extract the carrier and acceptor depth profiles and compare the results with experimental findings.